U.S. patent application number 13/614864 was filed with the patent office on 2013-06-13 for pulse width modulation controller.
This patent application is currently assigned to KIA MOTORS CORPORATION. The applicant listed for this patent is Jong Hoon Chae, Sang Hyun Jang, Ho Deuk Song. Invention is credited to Jong Hoon Chae, Sang Hyun Jang, Ho Deuk Song.
Application Number | 20130147414 13/614864 |
Document ID | / |
Family ID | 48464890 |
Filed Date | 2013-06-13 |
United States Patent
Application |
20130147414 |
Kind Code |
A1 |
Jang; Sang Hyun ; et
al. |
June 13, 2013 |
PULSE WIDTH MODULATION CONTROLLER
Abstract
Disclosed herein is a Pulse Width Modulation (PWM) controller.
The PWM controller includes a plurality of Field Effect Transistors
(FETs) and an FET driver. A comparator compares a current flowing
through the FETs with an overcurrent reference value, and
microcomputer controls a motor and a circuit protection function,
and turns off the FET driver when the current flowing through the
FETs is greater than the overcurrent reference value as a result of
comparison by the comparator.
Inventors: |
Jang; Sang Hyun; (Yongin,
KR) ; Song; Ho Deuk; (Seoul, KR) ; Chae; Jong
Hoon; (Hwaseong, KR) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Jang; Sang Hyun
Song; Ho Deuk
Chae; Jong Hoon |
Yongin
Seoul
Hwaseong |
|
KR
KR
KR |
|
|
Assignee: |
KIA MOTORS CORPORATION
Seoul
KR
HYUNDAI MOTOR COMPANY
Seoul
KR
|
Family ID: |
48464890 |
Appl. No.: |
13/614864 |
Filed: |
September 13, 2012 |
Current U.S.
Class: |
318/519 ;
323/284 |
Current CPC
Class: |
H02P 27/08 20130101;
H02H 7/085 20130101; H02H 7/0833 20130101 |
Class at
Publication: |
318/519 ;
323/284 |
International
Class: |
H02P 7/29 20060101
H02P007/29; G05F 1/565 20060101 G05F001/565 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 9, 2011 |
KR |
10-2011-0131876 |
Claims
1. A Pulse Width Modulation (PWM) controller, comprising: a
plurality of Field Effect Transistors (FETs) and an FET driver; a
comparator configured to compare a current flowing through the FETs
with an overcurrent reference value; and a microcomputer configured
to control a motor and a circuit protection function, and
selectively turn off the FET driver when the current flowing
through the FETs is greater than the overcurrent reference value as
a result of the comparison by the comparator.
2. The PWM controller according to claim 1, wherein the overcurrent
reference value for the comparator is set based on which of FET of
the plurality of FETs has a largest capacity.
3. The PWM controller according to claim 1, wherein the comparator
is configured to determine that the current flowing through the
FETs is greater than the overcurrent reference value when both
terminals of the motor are short circuited.
4. The PWM controller according to claim 1, wherein the comparator
is configured to determine that the current flowing through the
FETs is greater than the overcurrent reference value when a
negative terminal of the motor and a bias voltage terminal of a
battery are short circuited.
5. The PWM controller according to claim 1, wherein the plurality
of FETs comprise a low-side FET and a high-side FET.
6. The PWM controller according to claim 5, wherein the overcurrent
reference value for the comparator is set based on a capacity of
the low-side FET.
7. The PWM controller according to claim 6, wherein the comparator
is configured to determine that current flowing through the
low-side FET is greater than the overcurrent reference value when
both terminals of the motor are short circuited.
8. The PWM controller according to claim 6, wherein the comparator
is configured to determine that current flowing through the
low-side FET is greater than the overcurrent reference value when a
negative terminal of the motor and a bias voltage terminal of a
battery are short circuited.
9. A Pulse Width Modulation (PWM) controller, comprising: a
plurality of Field Effect Transistors (FETs) and an FET driver; a
comparator configured to compare a current flowing through the FETs
with an overcurrent reference value; a microcomputer configured to
control a motor and a circuit protection function; and a switch
configured to cut off a connection between the microcomputer and
the FET driver when the current flowing through the FETs is greater
than the overcurrent reference value as a result of comparison by
the comparator.
10. The PWM controller according to claim 9, wherein the
overcurrent reference value for the comparator is set based on
which of FET of the plurality of FETs has a largest capacity.
11. The PWM controller according to claim 9, wherein the comparator
is configured to determine that the current flowing through the
FETs greater than the overcurrent reference value when both
terminals of the motor are short circuited.
12. The PWM controller according to claim 9, wherein the comparator
is configured to determine that the current flowing through the
FETs greater than the overcurrent reference value when a negative
terminal of the motor and a bias voltage terminal of a battery are
short circuited.
13. The PWM controller according to claim 9, wherein the plurality
of FETs comprise a low-side FET and a high-side FET.
14. The PWM controller according to claim 13, wherein the
overcurrent reference value for the comparator is set based on a
capacity of the low-side FET.
15. The PWM controller according to claim 14, wherein the
comparator is configured to determine that current flowing through
the low-side FET is greater than the overcurrent reference value
when both terminals of the motor are short circuited.
16. The PWM controller according to claim 14, wherein the
comparator is configured to determine that current flowing through
the low-side FET is greater than the overcurrent reference value
when a negative terminal of the motor and a bias voltage terminal
of a battery are short circuited.
17. A non-transitory computer readable medium containing program
instructions executed by a PWM controller, the computer readable
medium comprising: program instructions that compare a current
flowing through a plurality of Field Effect Transistors (FETs) with
an overcurrent reference value; program instructions that control a
motor and a circuit protection function; and program instructions
that selectively turn off a FET driver when the current flowing
through the plurality of FETs is greater than the overcurrent
reference value as a result of the comparison.
18. The non-transitory computer readable medium according to claim
17, wherein the overcurrent reference value for the comparator is
set based on which of FET of the plurality of FETs has a largest
capacity.
19. The non-transitory computer readable medium according to claim
17, further comprising program instructions that determine that the
current flowing through the FETs is greater than the overcurrent
reference value when both terminals of the motor are short
circuited.
20. The non-transitory computer readable medium according to claim
17, further comprising program instructions that determine that the
current flowing through the FETs is greater than the overcurrent
reference value when a negative terminal of the motor and a bias
voltage terminal of a battery are short circuited.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] The present application claims priority to Korean Patent
Application No. 10-2011-0131876 filed on Dec. 9, 2011, the entire
contents of which is incorporated herein for purposes by this
reference.
BACKGROUND
[0002] 1. Field of the Invention
[0003] The present invention relates to a Pulse Width Modulation
(PWM) controller, configured to protect power terminals or signal
lines against shorts that may occur in a motor controller, without
requiring a separate element to do so, thus decreasing the price of
the motor controller and improving the reliability of the motor
controller.
[0004] 2. Description of the Related Art
[0005] Motor controllers, which are currently used for the blower
motor or the like of a vehicle, are of the linear control type and
typically perform control using a single large-capacity Field
Effect Transistor (FET). Since these motor controllers have a
large-capacity FET, they are designed so that even when a short
circuit occurs in the power line and the signal line of an FET
controller, the FET is not broken down and the internal temperature
element thereof, however, is broken down.
[0006] Further, since these motor controllers use only a single
FET, they have a simplified configuration and are easily
controlled. However, the power dissipation increases in these motor
controllers. When power dissipation increases, fuel efficiency
decreases during operation of, e.g., an air conditioner. Thus,
research has been conducted into an object which is able to reduce
power dissipation and improve fuel efficiency using a Pulse Width
Modulation (PWM) control scheme. When a PWM control scheme is used,
however, in a motor controller, the price of the overall controller
increases, because a short circuit protection function must be
applied using an FET which has a suitable capacity and logic
instead of a large capacity FET. FIG. 2 is a graph illustrating the
current flowing through a PWM controller and FIG. 3 is a circuit
diagram illustrating a conventional PWM controller. Referring to
FIG. 2, the current may have a normal state, an overcurrent state
and a short state. As can be seen from the graph, the current of
the PWM controller has the tendency to increase depending on the
duty ratio. As shown in FIG. 3, when both terminals of a motor are
short circuited because of worker error or the like, an overcurrent
flows therethrough and then a low-side FET L may bum when the
low-side FET L is turned on. Therefore, when it is determined by a
current sensor that an overcurrent is flowing therethrough, the
low-side FET L must be forcibly turned off during the time period
in which the low-side FET to L can resist the overcurrent.
Typically, this time is several tens of microseconds or less.
Therefore, a method of stably implementing such an overcurrent
protection circuit at a low cost is required.
[0007] The foregoing is intended merely to aid in the better
understanding of the background of the present invention, and is
not intended to mean that the present invention falls within the
purview of the related art that is already known to those skilled
in the art.
SUMMARY
[0008] Accordingly, the present invention has been made keeping in
mind the above problems, and an object of the present invention is
to provide a pulse width modulation (PWM) controller, which enables
implementation of a function for protecting power terminals or
signal lines against short circuits that may occur in a motor
controller without requiring a separate element to do so, thus
decreasing the price of the motor controller and improving the
reliability of the motor controller in the process.
[0009] In order to accomplish the above object, the present
invention provides a Pulse Width Modulation (PWM) controller that
includes a plurality of Field Effect Transistors (FETs) and an FET
driver; a comparator configured to compare a current flowing
through the FETs with an overcurrent reference value; and a
microcomputer configured to perform a function of controlling a
motor and a circuit protection function, and to turn off the FET
driver when the current flowing through the FETs is greater than
the overcurrent reference value as a result of a comparison by the
comparator.
[0010] Further, the present invention provides another Pulse Width
Modulation (PWM) controller, including a plurality of Field Effect
Transistors (FETs) and an FET driver; a comparator configured to
compare a current flowing through the FETs with an overcurrent
reference value; a microcomputer configured to control a motor and
a circuit protection function; and a switch configured to cut off a
connection between the microcomputer and the FET driver when the
current flowing through the FETs is greater than the overcurrent
reference value as a result of a comparison by the comparator.
[0011] Preferably, the overcurrent reference value for the
comparator may be set based on an FET having a largest capacity.
The comparator may determine that the current flowing through the
FETs is greater than the overcurrent reference value when both
terminals of the motor are short circuited. Alternatively, the
comparator may determine that the current flowing through the FETs
is greater than the overcurrent reference value when a negative
terminal of the motor and a bias voltage terminal of a battery are
short circuited.
[0012] Preferably, the plurality of FETs may include a low-side FET
and a high-side FET, and the overcurrent reference value for the
comparator may be set based on a capacity of the low-side FET. In
this case, the comparator may determine that current flowing
through the low-side FET is greater than the overcurrent reference
value when both terminals of the motor are short circuited. The
comparator may also determine that current flowing through the
low-side FET is greater than the overcurrent reference value when a
negative terminal of the motor and a bias voltage terminal of a
battery are shorted.
[0013] The above described PWM controller allows for protection of
power terminals or signal lines against short circuiting that may
occur in a motor controller without requiring a separate element to
do so, thus decreasing the price of the motor controller and
improving the reliability of the motor controller.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] The above and other objects, features and advantages of the
present invention will be more clearly understood from the
following detailed description taken in conjunction with the
accompanying drawings, in which:
[0015] FIG. 1 is a circuit diagram illustrating a PWM controller
according to an exemplary embodiment of the present invention;
[0016] FIG. 2 is a graph illustrating current flowing through the
PWM controller; and
[0017] FIG. 3 is a circuit diagram illustrating a conventional PWM
controller.
DETAILED DESCRIPTION
[0018] Hereinafter, a PWM controller according to embodiments of
the present invention will be described in detail with reference to
the attached drawings.
[0019] It is understood that the tem "vehicle" or "vehicular" or
other similar term as used herein is inclusive of motor vehicles in
general such as passenger automobiles including sports utility
vehicles (SUV), buses, trucks, various commercial vehicles,
watercraft including a variety of boats and ships, aircraft, and
the like, and includes hybrid vehicles, electric vehicles,
combustion, plug-in hybrid electric vehicles, hydrogen-powered
vehicles and other alternative fuel vehicles (e.g. fuels derived
from resources other than petroleum).
[0020] Furthermore, the control logic of the present invention may
be embodied as non-transitory computer readable media on a computer
readable medium containing executable program instructions executed
by a processor, controller or the like. Examples of the computer
readable mediums include, but are not limited to, ROM, RAM, compact
disc (CD)-ROMs, magnetic tapes, floppy disks, flash drives, smart
cards and optical data storage devices. The computer readable
recording medium can also be distributed in network coupled
computer systems so that the computer readable media is stored and
executed in a distributed fashion, e.g., by a telematics server or
a Controller Area Network (CAN).
[0021] FIG. 1 is a circuit diagram illustrating a PWM controller
according to an exemplary embodiment of the present invention. The
PWM controller of the present invention includes a plurality of
Field Effect Transistors (FETs) and an FET driver 500, a comparator
400, and a microcomputer 200. The comparator 400 compares a current
flowing through the FETs with an overcurrent reference value. The
microcomputer 200 controls a motor M and a circuit protection
function, and turns off the FET driver 500 when the current flowing
through the FETs is greater than the overcurrent reference value as
a result of the comparison by the comparator 400.
[0022] Generally, in the case of a Metal-Oxide-Semiconductor
Field-Effect Transistor (MOS FET), a diode component is
structurally present in a direction from a source to a drain when
the MOS FET is operated at high frequency. Therefore, when a
switching element is implemented as a MOS FET, a diode that
typically is required to be connected in parallel to the switching
element may be omitted, thus simplifying the construction of the
circuit. Further, when an FET is turned on, the drain (load) and
the source thereof are electrically connected to each other, so
that current may flow bidirectionally. However, when the FET is
turned off, current cannot flow from the drain to the source.
Current can, however, flow through a parasitic diode from the
source to the drain.
[0023] The present invention can be applied to the MOS FET, and is
intended to prevent the disconnection of a circuit from occurring
when, as in the circuit shown in the drawing, a short (case A)
occurs between both terminals M+ and M- of the motor M and a short
(case B) occurs between the negative terminal M- of the motor M and
the bias voltage terminal VS of a battery.
[0024] Conventionally, a separate high-capacity FET is typically
provided and is used to implement a protection circuit. However, in
the present invention, the comparator 400 for comparing the current
flowing through the FETs with the overcurrent reference value is
set instead, and the microcomputer 200 controls the motor M and the
circuit protection function. In this case, a pre-FET driver is set
to turn off the FET driver 500 when the current flowing through the
FETs is greater than the overcurrent reference value as a result of
the comparison by the comparator 400, thus performing a protection
function.
[0025] As shown in FIG. 2, each FET has a tendency for a current to
increase as the duty ratio of the FET increases, and the current
corresponding to a predetermined level has a threshold level as an
overcurrent. Therefore, when such an overcurrent is initially
detected and a signal is interrupted using the characteristics of
the FET, the circuit may be protected when shorts corresponding to
the illustrated case occur.
[0026] In detail, as shown in FIG. 1, the plurality of FETs
according to the present invention may be composed of a low-side
FET L and a high-side FET H, and the motor M may be operated in
response to the ON/OFF operations of the low-side FET L. Further,
since current flows through a shunt resistor only when the low-side
FET L is turned on, the current flows into the comparator 400 at
that time. Meanwhile, the high-side FET H is an FET functioning to
form a pass through which energy flows into the motor M when the
low-side FET L is turned off (that is, during an interval in which
power is not applied to the motor M so as to control the speed of
the motor M). In some cases, the high-side FET H may be implemented
as a diode for the sake of cost reduction, ease of control, etc.
Unless this pass is formed, a high reverse voltage may be induced
in the motor M and then the low-side FET L may be broken down when
the low-side FET L is turned off. Accordingly, the overcurrent
reference value for the comparator 400 may be set based on the
capacity of the low-side FET L.
[0027] When both the terminals M+ and M- of the motor M are short
circuited, the comparator 400 determines that current flowing
through the low-side FET L is greater than the overcurrent
reference value. Alternatively, when the negative terminal M- of
the motor M and the bias voltage terminal VS of the battery are
short circuited, the comparator 400 also determines that the
current flowing through the low-side FET L is greater than the
overcurrent reference value.
[0028] The above described functions may also be performed by
another exemplary embodiment of the present invention. A PWM
controller according to another embodiment of the present invention
includes a plurality of FETs and an FET driver 500, a comparator
400, a microcomputer 200, and a switch 300. The comparator 400
compares a current flowing through the FETs with an overcurrent
reference value. The microcomputer 200 performs a motor control
function and a circuit protection function. Finally, the switch 300
cuts off a connection between the microcomputer and the FET driver
when the current flowing through the FETs is greater than the
overcurrent reference value as a result of the comparison by the
comparator.
[0029] In this case, the switch 300 is configured to cut off the
connection between the microcomputer and the FET driver when the
current flowing through the FETs is greater than the overcurrent
reference value as a result of the comparison by the comparator,
thus protecting the circuit by disconnecting the microcomputer from
the FET driver.
[0030] Further, the PWM controller of the present invention may set
the overcurrent reference value for the comparator 400 based which
FET has the largest capacity, thus enabling the protection function
to be more stably and conservatively implemented.
[0031] Furthermore, the comparator 400 may enable a separate
high-capacity FET to be omitted by determining that the current
flowing through the FETs is greater than the overcurrent reference
value when both terminals M+ and M- of the motor M are short
circuited, or by determining that the current flowing through the
FETs is greater than the overcurrent reference value when the
negative terminal M- of the motor M and the bias voltage terminal
VS of the battery are short circuited.
[0032] Meanwhile, the PWM controller of the present invention may
incidentally implement a protection function even when any one of
the following short circuiting events occur:
[0033] (1) A PWM/Diagnosis short: a PWM/Diagnosis short occurs when
a PWM signal from a main controller is input as a Diagnosis signal
to the main controller, so that the main controller can determine
that a PWM signal line and a Diagnosis signal line have been short
circuited.
[0034] (2) A PWM/Vbatt(VS) short: when a PWM signal line and a
Vbatt line are short circuited, the input of the PWM controller
always has a duty ratio of 0%. In this case, since the duty ratio
is always 0%, the PWM controller is not damaged, and it can be
sensed that an abnormality has occurred in the motor.
[0035] (3) A PWM/GND short: in this case, the input of the PWM
controller always has a duty ratio of 100%, the PWM controller is
not damaged, and the motor always moves at the highest speed, and
thus it can be sensed that an abnormality has occurred in the
motor.
[0036] (4) A PWM/M+ short: this case is identical to that of the
PWM/Vbatt short.
[0037] (5) A Diagnosis/Vbatt short: in this case, a Diagnosis
signal always has a duty ratio of 0%. When the protection function
of the PWM controller, such as protection against overvoltage,
overcurrent, low voltage or high temperature, is operated, the main
controller cannot receive a Diagnosis signal, and thus the main
controller cannot determine whether the PWM controller is
defective. However, since the motor is not moving due to the
operation of the protection function of the PWM controller, whether
an abnormality has occurred may be sensed. As a result, damage does
not occur in the PWM controller.
[0038] (6) A Diagnosis/GND short: in this case, since a Diagnosis
signal always has a duty ratio of 100% (low), the main controller
may sense whether an abnormality has occurred, and then stop the
PWM controller accordingly.
[0039] (7) A Diagnosis/M+ short: this case is identical to that of
the Diagnosis/Vbatt short.
[0040] (8) A Diagnosis/M- short: in this case, the voltage level of
the M- terminal is the inverse of a PWM input signal. When the
voltage of the M- terminal is input as a Diagnosis signal to the
main controller, the main controller may determine that an
abnormality has occurred in the PWM controller. In this case, the
PWM controller is not damaged, and it can be determined whether an
abnormality has occurred in the motor.
[0041] (9) A Vbatt(VS)/GND short: in this case, the PWM controller
is not damaged, but a fuse melts due to the short that occurred at
the power terminal.
[0042] Accordingly, the above described PWM controller(s) having
the above-described construction protect power terminals or signal
lines against the short circuiting that may occur in a motor
controller without requiring a separate element to do so, thus
decreasing the price of the motor controller and improving the
reliability of the motor controller.
[0043] Although the preferred embodiments of the present invention
have been disclosed for illustrative purposes, those skilled in the
art will appreciate that various modifications, additions and
substitutions are possible, without departing from the scope and
spirit of the invention as disclosed in the accompanying
claims.
* * * * *